Correct, the liquid crystals are between two polaroid filters that are cross polarized. The liquid crystal between the filters rotates the plane of the polarized light causing the light to be able to go through the top filter. When a voltage is applied to the liquid crystal, it no longer rotates the plane of the polarized light and the display looks black because the top filter blocks the polarized light.
A lot of ordinary compounds will rotate the plane of polarized light that shines through them. Put these in between two crossed polarized filters and they will cause light that went through them to pass through the second filter, with colorful effects because different wavelengths are affected differently. If you have two polaroid filters handy, cross them so they don’t transmit light and then put a clear plastic fork or sugar crystals between them.
I used to work at an automotive glass plant. The marks you see are mold marks. For the most part all car glass other than the windshield is tempered. That’s why it breaks the way it does. The windshield is not. It as many noted is two pieces with vinyl in between. That helps absorb impacts etc. to mold windshields you can put them on a frame of the desired shaft and put them through an oven and let gravity do the work or put them through an over and then place the hot glass on a vacuum form. Similar with rear windows also known as back lights. I only ever saw windshields done with the gravity sag method. Anyway an artifact of the molding process are those diamonds you see.
It was once suggested that if windshields were linearly polarized in the direction from lower left to upper right, and if headlights were similarly polarized, the glare from approaching headlights would be reduced (but not eliminated) whereas the return from the drivers’ own headlights would not be attenuated (because reflection does not alter the direction of linear polarization).
On the other hand, reflection of circularly polarized radiation DOES change direction (from left-handed to right handed and vice versa) when reflected from the rear surface of a rain drop (after the radiation passes through the water of an individual droplet). For this reason aircraft radars transit circularly polarized radiation. (The antenna of a left-handed transmitting radar has about -20 db less gain for right-handed received signals than it does “for its own kind” and vice versa.)
For some reason light reflected from the shells of many scarabs is left-handed circularly polarized, and I believe light from summer lightning bugs is circularly polarized as well.
Light from galactic stars is slightly linearly polarized, because the galactic dust through which it passes is not spherical but slightly elongated with the long axis of the dust particle aligned with the galactic magnetic field, and this anisotropy in particle orientation attenuates one plane of polarization more than the other. This phenomenon has allowed the magnetic field of out Milky Way galaxy to be mapped.
It is often easier mathematically to imagine a radiation field vector (either the electric or the magnetic field) to consist of two orthogonal vectors: if the vectors are of equal magnitude and in phase, the resulting field appears as linearly polarized; if the vectors are of equal magnitude but have a ±90º phase difference, the wave appears as circularly polarized, either left or right depending upon the sign of the difference; and if their magnitudes are unequal with a 90º phase difference, the radiation is said to be elliptically polarized.
In quantum mechanics, polarization is just the manifestation of the photon’s angular (spin) momentum.
My mistake…I’m guessing you’re young…Polaroid/TVs makes no sense to me, but I guess they’ve sold their name for use on whatever…while not knowing they made sunglasses makes you late 20s, max, I’m guessing…
Edwin Land was one of our countries greatest inventors.
He invented the plastic polarizing sheet used in sunglasses and camera filters, then founded the Polaroid corporation.
He then invented a system for instant photography and called it Polaroid too.
I was a glassblower for 25 years. We used 2 polarized lenses to identify thermal stress in glass sculptures. This is called a “Polariscope” when you place a piece of glass between two polarized lenses. You can then see the stress patterns in a piece of glass. As a glassblower we wanted the glass to be free of stress, using a process called annealing, done in an oven/ kiln. After annealing we would use a makeshift polariscope to check for stress.
In the case of a car window the stress was installed intentionally so the glass in a car accident will shatter into tiny small pieces and not create sharp jagged chards of glass.
When certain freak conditions exist your polarized sunglasses become a polariscope and you see the stress pattern in the glass.
When certain freak conditions exist your polarized sunglasses become a polariscope and you see the stress pattern in the glass.
I was a glassblower for 25 years. We used 2 polarized lenses to identify thermal stress in glass sculptures. This is called a “Polariscope” when you place a piece of glass between two polarized lenses. You can then see the stress patterns in a piece of glass. As a glassblower we wanted the glass to be free of stress, using a process called annealing, done in an oven/ kiln. After annealing we would use a makeshift polariscope to check for stress.
In the case of a car window the stress was installed intentionally so the glass in a car accident will shatter into tiny small pieces and not create sharp jagged chards of glass.